Disk drives comprise a disk and a head connected to a distal end of an actuator arm which is rotated about a pivot by a voice coil motor (VCM) to position the head radially over the disk. The disk comprises a plurality of radially spaced, concentric tracks for recording user data sectors and servo sectors. The servo sectors comprise head positioning information (e.g., a track address) which is read by the head and processed by a servo control system to control the velocity of the actuator arm as it seeks from track to track.
A disk drive typically comprises a boot read only memory (ROM) for storing boot code used to boot the disk drive when initially powered on. The boot code typically includes a disk initialization procedure to enable control circuitry to read additional boot code form the disk. The boot code read from the disk typically includes a volatile semiconductor memory (VSM) initialization procedure to initialize a VSM such as a double data rate (DDR) random access memory (RAM). Once the VSM is initialized, the remaining boot code is read from the disk into the VSM and then executed from the VSM in order to finish booting the disk drive.